Here's how I think it would go down:
Godzilla enters the fray, stomping and breathing powerful atomic breath. Predator has gone all camo-invisible and is scoping out this beast, clearly a prize worth taking. Jon Irenicus and Sauron both immediately cast some protective shields around themselves and thus recognize each other as dark magicians. They begin ignoring everybody around them while they carry on a lengthy argument about who should join whom in their quest to take over the world. Kabuto has been flipped over onto his back by Godzilla's stomps and lays there useless and unnoticed for a while. The Transcendent One has risen into the air and begun casting gigantic hurled-from-space magic missiles at Godzilla. With all the magic and nuclear stuff flying around, the Alien just gets caught and blasted apart, spraying acid everywhere, killing Kabuto, further disfiguring Jon Irenicus, and casting Sauron out of his latest mortal frame. Meanwhile, the three AIs have been casting around invisibly, looking for some hardware to take control of. The only hardware available is the Predator's suit mechanics. So, just as Predator has devised a strategy for attacking Godzilla, his suit betrays him, he begins flashing visible/invisible as the AIs fight for control. He leaps onto Godzilla's back to avoid the atomic blasts, and his explosives go off, killing him but reinvigorating Godzilla with nuclear energy. With the AIs out of the way, Jon Irenicus, a disembodied Sauron, and the Transcendent One are faced with an over-energized Godzilla, who does not respond to their evil seductions. (The AIs are merely powerless disembodied intelligences now, so... out of the fight. Sauron howls in evil frustration and flees to the netherworld to regather his power over the next several centuries. Irenicus decides the Transcendent One, being a mortality severed from the mortal form, is the way to go, if you want to rule things forever. So, taking a chance, he attempts to sever himself from his own mortality by leaping into Godzilla's nuclear breath. Doesn't work. Irenicus is down for the count. The Transcendent One just wants to be left alone, so he cloaks himself in invisibility and remains silent. Without a foe left to fight, Godzilla quiets down and stalks out alone, howling in existential monster outcast pain.
The Transcendent One has faded into his own dimension rather than stick around to claim his prize as victor, and no one seems to think it a good idea to follow Godzilla, so the prize is awarded to the disabled children of the city and the prize money donated to nuclear contamination cleanup at the site of the battle royale.